Distinctive characteristics of Archaea • Cell wall • Lipids/membrane • Information processing • Physiological adaptations to extreme environments
Distinctive characteristics ofArchaea
• Cell wall• Lipids/membrane• Information processing• Physiological adaptations to extreme
environments
Pseudomurein
Fig. 20.2 Substitutes for N-Acetylmuramic acid (NAM) of peptidoglycan
Fig. 20.1
Gram+ vs. Gram- ArchaeaGram+Cell wall of pseudomurein orother complex carbohydrate
Gram-No outer membraneNo cell wallThick protein/glycoprotein coat
Archaeal Lipids
• Fatty acid attached by ethernot ester links
• Varying lengths of carbonside chains- 20 or 40 carbon
Fig. 20.3
Flexible
Rigid-givesmembranestability tothermophiles
Fig. 20.5
ArchaeaSimilarities to prokaryotes• Size• Shape• Lack nucleus• Single chromosome• Genes in operons• No introns
Similarities to eukaryotes• Few plasmids• RNA
polymerase/promoters• Translation machinery:
ribosome and tRNA
Sequencing of Methanococcus jannaschii in 199256% of genes not similar to bacteria or eukaryotes!
Major groups of Archaea
• Methanogenic archaea• Archaeal sulfate reducers• Extremely halophilic archaea• Cell wall-less archaea• Extremely thermophilic S0-metabolizers
Methanogens
• Largest group of Archaea• Form methane (CH4) from CO2 or other
compounds (e.g. formate, methanol, acetate)• Strict anaerobes• Found in a variety of anaerobic environments rich
in organic matter• Causes cows to belch!• Methane: energy source vs. greenhouse gases
Fig. 20.12
Fig. 20.10
Sulfate-reducing archaea
• Only genus is Archaeoglobus• Reduces sulfates to produce
sulfide (H2S)• Extremely thermophilic
(optimum=83˚C)• Strictly anaerobic• Isolated from a deep sea
thermal vent
Extremely thermophilic S0-metabolizers
• Obligately thermophilic(70-110˚C)
• Mainly strict anaerobes• Can be acidophilic• S0 reduce to sulfide• Hot springs of
Yellowstone
Extreme halophiles
• Require high NaCl concentration– Require 1.5 M, optimum 3-4 M
• Primarily aerobic• Carotenoids give reddish color• Bacteriorhodopsins capture light for energy in
anaerobic respiration
Cell wall-less archaea
• Thermoplasma and Picrophilaceae• Resistant to antibiotics• Like warm, acidic environments• Thermoplasma isolated from coal refuse piles
– 55-59˚C, pH 1-2• Picrophilaceae can grow at pH=0